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PRODUCT SPECIFICATION
RC5050
17
Inductor Location.
The inductor should be located near to the Source of the
Power MOSFET. The ideal condition would be to use an
internal power plane to connect the Source of the power
MOSFET, the inductor, and the flyback schottky diode
together.
Sense Resistor.
– The sense resistor should be located next to the
inductor.
– The two traces that run from the sense resistor to the
RC50XX controller IC should be minimum width
traces and be run parallel to each other. We
recommend these sense resistor values:
For Pentium Pro use 0.006
W
.
For P55C MMX Pentium/ AMD K6 use 0.007
W
.
For Pentium II use 0.006
W
.
Ground Plane.
The RC50XX controller IC have a continuous ground
plane running underneath the entire chip area. Each of the
IC ground pins should have a separate via connection
down into the ground plane.
Input Filter.
In many high current DC-DC converter designs, it is
advisable to add an input inductor in order to create an
input filter. An inductor on the order of 1-3uH is usually
all that is required to perform the filter. When this
component is added to the circuit, it is important that the
RC50XX controller IC receive its VCC power from the
system side of the input inductor and not the “dirty” side
of the inductor. (ie the side that is connected to the power
MOSFET drains)
To Minimize Electromagnetic Interference (EMI).
– Avoid long ground connections. Connect directly to
the ground plane.
– Use a star ground, where all grounds are connected to
one point.
– Use good quality inductors such as torrids or pot cores.
Avoid rod inductors.
– Route the high current carrying traces as power planes
where possible.
– Keep sensitive low-level signals away from the active
switching components. Try to route them using the
ground plane as a shield.
Example of a PC Motherboard Layout and
Gerber File
A reference design for motherboard implementation of the
RC5050 along with the Layout Gerber File and Silk Screen
are presented below. The actual PCAD Gerber File can be
obtained from a Fairchild Semiconductor local Sales Office
or from Marketing at 650-966-7734.
RC5050 Evaluation Board
Fairchild Semiconductor provides an evaluation board for
the purpose of verifying the system level performance of the
RC5050. The evaluation board serves as a guide as to what
can be expected in performance with the supplied external
components and PCB layout. Please call your local Sales
Office or Fairchild Semiconductor Marketing department at
650-966-7734 for an evaluation board.